Kayla Martin

The impact of accretion on post-AGB binary star evolution

Post-AGB stars in binaries have quickly become a topic of much interest, largely due to their observed peculiar surface chemistry and unique wide range of orbital periods (~100-2000 days) and eccentricities (0 to ~0.6). Post-AGB stars are often found dancing in orbit with a main sequence companion and are further observed to be surrounded by a dusty circumbinary disk. These objects have recently left the turbulent AGB phase after experiencing significant, rapid mass-loss driven by binary interaction. The exact evolutionary pathway and mechanisms responsible for producing the observational properties of these systems remains unclear, and clearly deviates from classical binary evolution scenarios. In this study, we use the open-source 1D stellar evolution code MESA to simulate the accretion of metal-poor gas from a circumbinary disk onto an evolving post-AGB star, to examine the formation of chemical depletion patterns in post-AGB star photospheres. Further, we explore the impact of accretion on the structural evolution of post-AGB stars, as well as the timescale of post-AGB evolution, which may have important consequences on the formation of complex planetary nebulae.